On the Frequency of Gas Giant Planets in the Metal-Poor Regime Alessandro Sozzetti 1, D.W. Latham 2, G. Torres 2, R.P. Stefanik 2, S.G. Korzennik 2, A.P.

On the Frequency of On the Frequency of Gas Giant Planets Gas Giant Planets in the Metal-Poor in the Metal-Poor

RegimeRegimeAlessandro Sozzetti1,

D.W. Latham2, G. Torres2, R.P. Stefanik2, S.G. Korzennik2, A.P. Boss3, B.W. Carney4, J.B. Laird5

(1) INAF/OATo - (2) CfA - (3) CIW - (4) UNC - (5) BGSU

Pisa, 6 MayPisa, 6 May 2009 2009

Core Accretion & Core Accretion & Disk InstabilityDisk Instability

** Core Accretion: Core Accretion: Bottom-Up!Bottom-Up!Accumulate a 10 MAccumulate a 10 M core (dust to core (dust to planetesimals to runaway accretion), planetesimals to runaway accretion), which accretes a massive gaseous which accretes a massive gaseous envelope from the disk.envelope from the disk.

** Disk Instability: Disk Instability: Top-Down!Top-Down!Local gravitational collapse of a Local gravitational collapse of a gaseous portion of the disk leads to a gaseous portion of the disk leads to a Jupiter-mass (or larger) protoplanet. Jupiter-mass (or larger) protoplanet. The rocky core is formed almost The rocky core is formed almost simultaneously by sedimentation of simultaneously by sedimentation of dust grains to the center.dust grains to the center.

Boss (SSRv, 2005)Boss (SSRv, 2005)


Ida & Lin (ApJ, 2004), Kornet et al. (A&A, 2006):“The frequency of giant planet formation by core

accretion is roughly a linear function of Z”

Boss (ApJL, 2002): “The frequency of giant planet formation by disk instability is

remarkably insensitive to Z”

N/AN/A

Do giant planets form by Core Accretion, Disk Instability, or both?Do giant planets form by Core Accretion, Disk Instability, or both?


HST/WFPC2HST/WFPC2

Globular Cluster 47 Tucanae

HST (WFPC2) observed about 34,000 stars in 47 Tuc, obtaining time series photometry over a period of 8.3 days

Gilliland Gilliland et. al. (ApJ et. al. (ApJ 2000), Weldrake et al. (ApJ 2005)2000), Weldrake et al. (ApJ 2005)

11 Gyr, 106 stars[Fe/H] ~ - 0.7

No planet eclipses were seen.No planet eclipses were seen.


However…However…

• Crowding can impact giant planet formation, migration, Crowding can impact giant planet formation, migration, and survivaland survival

• The absence of Hot Jupiters in a metal-poor environment The absence of Hot Jupiters in a metal-poor environment does not imply they don’t exist at larger radiidoes not imply they don’t exist at larger radii

GCs are not optimal Go to the fieldGCs are not optimal Go to the field


Fp vs [Fe/H]

Linear Dependence?Linear Dependence?Flat tail for [Fe/H] < 0.0?Flat tail for [Fe/H] < 0.0?Low statistics for [Fe/H] < -0.5Low statistics for [Fe/H] < -0.5

Santos et al. (A&A, 2004):Santos et al. (A&A, 2004):No P, K, [Fe/H] thresholds:No P, K, [Fe/H] thresholds:

FFpp ~ Z, for Z > 0.02) ~ Z, for Z > 0.02)FFpp ~ const, for Z < 0.02 ~ const, for Z < 0.02

Fischer & Valenti (ApJ, 2005):Fischer & Valenti (ApJ, 2005):K > 30 m/s, P < 4 yr, -0.5<[Fe/H]<0.5: K > 30 m/s, P < 4 yr, -0.5<[Fe/H]<0.5:

Quadratic dependence?Quadratic dependence?Flat tail for [Fe/H]<0.0?Flat tail for [Fe/H]<0.0?

Low statistics for [Fe/H] < -0.5Low statistics for [Fe/H] < -0.5

]/[0.210 HFepF


What is the dominant mode What is the dominant mode of giant planet formation?of giant planet formation?

Is FIs Fpp([Fe/H]) bimodal or monotonic?([Fe/H]) bimodal or monotonic?

Small-number statistics for [Fe/H] < -Small-number statistics for [Fe/H] < -0.5 prevents one from drawing 0.5 prevents one from drawing conclusions:conclusions:


Keck/HIRES Metal-Poor Planet SearchKeck/HIRES Metal-Poor Planet Search

• 200 stars200 stars from the Carney-Latham and Ryan samples from the Carney-Latham and Ryan samples • No close stellar companionsNo close stellar companions• Cut-offs: -2.0 < [Fe/H] < -0.6, TCut-offs: -2.0 < [Fe/H] < -0.6, T

effeff < 6000 K, V < 12 < 6000 K, V < 12• Reconnaissance for gas giant planets within 2 AUReconnaissance for gas giant planets within 2 AU• Campaign duration: 3 yearsCampaign duration: 3 years Sozzetti et al. (ApJ, 2006)Sozzetti et al. (ApJ, 2006)


The RV dispersion of the The RV dispersion of the fullfull sample peaks at 9 m/s sample peaks at 9 m/s

Sozzetti et al. (ApJ, 2006)Sozzetti et al. (ApJ, 2006)

effVV

RV Tt

t],Fe/H[F10

2/1

5.2/

exp

0 0


No clear RV trends are No clear RV trends are seen as a function of seen as a function of TTeffeff, [Fe/H], and , [Fe/H], and ΔΔTT


Analysis: MethodologyAnalysis: Methodology• Statistical analysis: testing for excess Statistical analysis: testing for excess

variability (F-test, variability (F-test, 22-test, Kuiper test)-test, Kuiper test)

• Analysis of long-term (linear and curved) trendsAnalysis of long-term (linear and curved) trends

• Limits on companion mass and period from Limits on companion mass and period from detailed simulationsdetailed simulations

• Upper limits on fUpper limits on fp p and new powerful constraints and new powerful constraints on fon fpp([Fe/H]) in the metal-poor regime([Fe/H]) in the metal-poor regime


About 6% of the stars About 6% of the stars in the sample have in the sample have long-period companionslong-period companions

Follow-up with direct infrared imaging Follow-up with direct infrared imaging (MMT/Clio) to determine their nature(MMT/Clio) to determine their nature(low-mass stars or brown dwarfs)(low-mass stars or brown dwarfs)

RV VariablesRV VariablesFollow-upFollow-up


MMT/Clio Imaging @ 5 MMT/Clio Imaging @ 5 μμmm

ΔΔM ~ 2.5 magM ~ 2.5 magΔΔM ~ 6.5 magM ~ 6.5 mag

~0.5”

~1”


COMPLETENESS:COMPLETENESS:

- 6 observations, 3-yr baseline;6 observations, 3-yr baseline;

- RV RV = 9 m/s= 9 m/s

- 99.5% confidence level99.5% confidence level

- Sensitivity to companions Sensitivity to companions withwith 1M1MJJ<M<Mppsin(i)<6Msin(i)<6MJ J (K > 100 (K > 100 m/s), m/s), with orbital periods between with orbital periods between a few days and 3 yearsa few days and 3 years

- Strong dependence of - Strong dependence of detection detection thresholds on eccentricitythresholds on eccentricityWE FIND NONE…WE FIND NONE…


For n=0, N=160:For n=0, N=160:

For n=1, N=160:For n=1, N=160:

Frequency of Close-in CompanionsFrequency of Close-in Companions(-2.0<[Fe/H]<-0.6, K > 100 m/s, P < 3 yr, e < 0.3)(-2.0<[Fe/H]<-0.6, K > 100 m/s, P < 3 yr, e < 0.3)


Compare with the SPOCS Compare with the SPOCS database: database:

b=0.99

b=1.05

b=0.89

KTeff 3337 dex03.004.0]/[ HFe

SUNMM 016.0002.0

((σσ = 134 K) = 134 K)

((σσ = 0.12 dex) = 0.12 dex)

((σσ = 0.06 M = 0.06 MSUNSUN))

Reliability of the Reliability of the Atmospheric ParametersAtmospheric Parameters


Sozzetti et al. 2009 (ApJ, in press):Sozzetti et al. 2009 (ApJ, in press):K > 100 m/s, P < 3 yr, -1.0<[Fe/H]<0.5:K > 100 m/s, P < 3 yr, -1.0<[Fe/H]<0.5: ?10 ]/[0.2 CF HFe

p


Summary• We observe a dearth of gas giant planets (K > 100 m/s) within 2

AU of metal-poor stars (-2.0 < [Fe/H] < -0.6), confirming and extending previous findings

• The resulting average planet frequency is Fp< 0.67% (1σ)

• Fp(-1.0<[Fe/H]<-0.5) appears to be a factor of several lower than

Fp([Fe/H]>0.0), but it’s indistinguishable from Fp(-0.5<[Fe/H]<0.0).

• Is Fp([Fe/H]) bimodal or not? It is consistent with being so. However, need larger and better statistics to really discriminate…

• 1) Expand the sample size; 2) lower the mass sensitivity threshold; 3) search at longer periods.

Next generation RV surveys and future high-precision space-borne astrometric observatories (Gaia, SIM-Lite) will help…

On the Frequency of Gas Giant Planets in the Metal-Poor Regime Alessandro Sozzetti 1, D.W. Latham 2, G. Torres 2, R.P. Stefanik 2, S.G. Korzennik 2, A.P.

Documents

stars feh

f p vs feh linear dependence

frequency of gas giant

core dust

giant planets form

poor stars

planet eclipses

rocky core